Ring phosphonates

ABSTRACT

A nine-membered ring phosphonate compound having the formula   WHEREIN R1 is hydrogen or methyl, R2 is phenyl or substituted phenyl wherein the substitution is one or more of halogen, nitro, lower alkyl, cyclohexyl, alkoxy, naphthoxy or phenyoxy and R3 and R4 are the same or different and are lower alkyl of up to eight carbon atoms, preferably methyl, is formed by the reaction of acrylic or methacrylic acid with a compound of the general formula   WHEREIN R2, R3 and R4 are as above. The ring phosphonates are useful for forming flame-retardant compositions from mixtures comprising the phosphonate and methyl methacrylate.

United States Patent [191 Clovis et al..

[ RING PHOSPHONATES [75] Inventors: James S. Clovis; Francis R.Sullivan,

both of Warminster, Pa.

[73] Assignee: Rohm and Hess Company,

Philadelphia, Pa.

[22] Filed: 4 May 3, 1971 [21] Appl. No.: 139,949

[52 U.S. Cl ..l 260/936, 260/458, 260/968 [51] lint. Cl. C01d 105/04,C08f 45/58 [58] Field of Search 260/936 [56] References Cited UNITEDSTATES PATENTS 2,944,074 7/1960 Atherton 260/936 Primary Examiner-AntonH. Sutto Attorney, Agent, or Firm-Michael B. Fein [57 ABSTRACT Anine-membered ring phosphonate compound having the formula [11]3,812,219 [451 May 21, W74

wherein R, R and R are as above. The ring phospho mates are useful forforming flame-retardant composi tions from mixtures comprising thephosphonate and methyl methacrylate.

3 Claims, N0 Drawings pounds.

1 RING PHOSPHONATES The present invention relates to novel ninememberedring phosphonate compounds, to a process a for making these compoundsand to acrylic compositions of superior flame-resistant properties. Theacrylic compositions comprise an addition polymer formed from a mixturecontaining the novel phosphonate com- The reaction of phosphites withunsaturated acids and esters is generally known. Drawing analogy fromthis prior art as exemplified by Topics in Phosphorus Chemistry, vol. 1,lnterscience (1964), pp. 92-94 and Structure and Mechanism inOrgano-Phosphorus Chemistry, Hudson, Academic Press 1965), PP- 192-196,it might be predicted that the reaction between a cyclic phosphite andan a-B-unsaturated acid such as acrylic or methacrylic would produceapolymeric product.

it has surprisingly been found in the present invention that anine-membered phosphonate compound of the general formula min: H, R

stituted phenyl wherein the substitution is one or more wherein R, R andR are as above. It has been found that these novel ring phosphonatecompounds are useful for forming flame resistant. compositions frommonomer mixtures comprising the phosphonate and methyl methacrylate.

It is particularly notable that the phosphonate com-- positions of thepresent invention exhibit excellent thermal stability. Thisproperty isof particular importance where the compositions are to be incorporatedinto molding powders for processing by extrusion and molding operations.Commonly used commercial flame-retardant phosphonate compositions suchas that prepared from ethylene chlorophosphite and acetone and thatprepared from acetaldehyde, ethylene oxide and PCl are not stable aboveabout 180C. while common processing temperatures for molding powders arenear 250. to 275C. The phosphonate compositions of the present inventionare advantageously thermally stable at these processing temperatures.

The cyclic phosphite used to prepare the products of the presentinvention may be prepared according to the procedure set out inHechenbleikner et al., US Pat.

No. 2,834,798, issued May 13, 1958. In the general formula given abovefor these phosphites it is preferred that R be phenyl and R and R bothbe methyl so that the preferred nine-membered ring phosphonate compoundsof this invention are 2-oxo-2-phenoxy-5-oxo- 8,8dimethyl-(l,6-dioxa-2-phosphacyclononane) and2-oxo-2-phenoxy-4-methyl-5-oxo- 8,8-dimethyl-( l ,6-dioxa-2-phosphacyclononane).

The acrylic compositions of the present invention may be, for example,an acrylic sheet material or an acrylic molding composition. The acryliccompositions of the present invention comprise an addition polymerformed from a mixture comprising; (a) at least 50 per cent by weight ofmethyl methacrylate, and (b) 5 to 30 percent by weight of aflame-retardant nine-membered ring phosphonate defined by the generalformula given supra. The mixture may additionally comprise l() to 20weight percent of a member selected from the class consisting ofisobornyl acrylate, isobornyl methacrylate and mixtures thereof and/orup to 25 weight percent of an ethylenically unsaturated acrylic compoundsuch as acrylic or methacrylic acid.

The acrylic composition of this invention may be formed by any processknown in the art such as for example those referred to and shown inForsyth, US. Pat. application, Ser. No. 819,484, filed Apr. 25, 1969. I

The addition polymer may constitute the entire body of the compositionor it may, for example, constitute the main body and serve as a binderin sheet form for common additives such as coloring dyes or pigments,release agents and other additives.

A preferred embodiment of this invention is an acrylic composition, themain body of which is an addition polymer formed from a mixturecomprising (a) 50 to weight percent methyl methacrylate, (b) 15 to 25weight percent of the flame-retardant, and (c) 10 to 20 weight percentisobornyl acrylate, isobornyl methacrylate or mixtures thereof. Anotherembodiment of this invention is an acrylic sheet, the main body of whichis an addition polymer formed from a. mixture comprising (a) at least 50weight percent of methyl methacrylate, (b) 10 to 30 weight percent ofthe flame-retardant, and

(c) 0.5 to 25 weight percent acrylic or methacrylic acid.

The ethylenically unsaturated acrylic monomer,-

which may be used inquantities up to 25 weight percent includesmonoethylenically unsaturated acrylic compounds and polyethylenicallyunsaturated acrylic compounds. These unsaturated acrylic compoundsconstitute a class of compounds known in the art and include but are notlimited to such compounds as methacrylic acid, acrylic acid, alkylesters and substituted alkyl esters of acrylic acid and methacrylicacids, such as ethyl acrylate, butyl acrylate, Z-ethylhexyl acrylate,isobutyl acrylate, isobutyl methacrylate, ethyl-thioethyl methacrylateor acrylate, isobutyl acrylate, halogenated alkyl methacrylate, glycidylmethacrylate and the like; and dior polyacrylic esters of cliols andpolyols, such as 1,3-butylene dimethacrylate,l,3-butylene diacrylate,trimethylolpropane trimethacrylate and the like; acrylic nitriles, suchas acrylonitrile, methacrylonitrile and the like. The inclusion of theseethylenically unsat urated acrylic compounds offers specialcharacteristics that are particularly useful in some end-useapplications. For example, the inclusion of methacrylic acid improvesphysical properties including the heat distortion temperature andclarity when some polymeric phosphorus compounds are utilizedin theinvention. The preferred amount of methacrylic acid is 0.5 to 5 percent.Polyethylenically unsaturated acrylic monomers or acrylic esters may beutilized to improve high temperature heat resistance and other physicalproperties. Generally, the-concentrations of the polyethylenicallyunsaturated monomers are maintained at a low level to allowthermoforming of the sheet or injection molding of molding powders. Theethylenically unsaturated acrylic monomers may be a mixture of two ormore of the compounds from the class.

To assist those skilled in the art in the practice of the presentinvention, the following modes of operation are set forth asillustrations, parts and percentages being by weight unless otherwisespecifically noted.

EXAMPLE 1 This example illustrates the preparation of a cyclic phosphiteuseful for preparing the nine-membered ring phosphonate compounds of thepresent invention.

One mole of 2,2-dimethyl-1,3-propanediol (neopentyl glycol) and one moleof triphenyl phosphite are mixed in a flask. The mixture is heatedgradually on an oil bath at 10 to 15 mm pressure; phenol distilling offthrough a small column. The product, 2-phenoxy-5,5-dimethyl-1,2,3-dioxaphosphorirane, having a 17 of 1.50375 is recoveredby distillation at 9095C. at lmm.

EXAMPLE 2 This example illustrates the preparation of the ninemem beredring phosphonate compounds of the present lIlVCnUOn.

A solution of 22.6 g. (0.1 mole) of the 2-phenoxy-5,5-dimethyl-1,2,3-dioxaphosphorirane of Example 1 and 7.2 g. (0.1) moleof acrylic acid (both freshly distilled) are dissolved in 29.8 g. ofreagent grade ethylene dichloride. The solution is degassed andblanketed with nitrogen. The solution temperature is maintained below25C. for about seven hours. After 22 hours, the

light yellow solution is concentrated and added to a 2:1

1 solution of etherzCCl, to give 15.8 g. of product, m.p.

wherein d) is phenyl. This compound is designated OPOD (DPCN) as anabbreviation for 2-oxo-2- phenoxy-5-oxo-8,8-dimethyl-(1,6-dioxa-2-phosphacyclononane).

EXAMPLES 3 to 9 This example illustrates the preparation of acrylicsheet material of the present invention.

A solution of 25 percent acetyl peroxide in dimethyl phthalate is addedto methyl methacrylate (MMA) to give a 0.03 percent concentration of theperoxide and methacrylate. The mixture is combined with the cyclicphosphonate, OPOD(DPCN), prepared in Example 1 in a ratio of 12.5 partsphosphonate and 87.5 parts MMA and with additives such as chainregulators, color dyes, lubricants and the like. The resulting mixtureis cured between glass plates. The cured cast sheets, 0.120 to 0.130inches thick are removed. Samples of the cast sheets are flame tested byASTM D 635- 56T. The cast sheet burns at a rate of 0.8 inches/minute.

The compositions indicated in the Table are prepared according to thepreceding procedure and are tested for flame advance, ASTM D 635-56T,with the results as indicated. The following abbreviations are used;methyl methacrylate (MMA); the nine membered ring phosphonate of Example2 [OPOD(DPCN)], isobornyl methacrylate (IBOMA), and tertiary-butylmethacrylate (t-BMA).

Table I Burning Rate Example Composition (Inches/minute) 3OPOD(DPCN)/MMA; 12.5/87.5 0.8 4 MMA; ercent 1.3 5 lBOMA/M A; 15/85 1.0 6lBOMA/MMA; 30/70 1.3 7 OPOD(DPCN)/MMA/1BOMA; 0.3

20/68/12 8 OPOD(DPCN)/MMA/t-BMA; 0.5

20/68/12 9 OPOD(DPCN)/MMA; 20/80 0.6

EXAMPLE 10 Two samples prepared from 2-phenoxy-5,5-

dimethyl-1,2,3-dioxaphosphorirane and methacrylic acid are prepared bythe procedures of Example 2. The first sample exhibits an acid number of38 which rises to 40 after 2 /& days at C; the second sample exhibits anacid number of 20 which rises to 36 after the same length of time at thesame temperature. A commercial flame-retardant prepared from ethylenechlorophosphite and acetone shows an acid number of about 6 which after2 /2 days at 180C. rises to 300 and a product of acetaldehyde, ethyleneoxide and PCl shows a first acid number of 6 and after the sametreatment exhibits a number of about 130. This example shows theimproved thermal stability of the products of the present inventioncompared to other known flameresistant compositions.

What is claimed is:

1. A nine-membered ring phosphonate compound of improved thermalstability having the general formula ERi wherein R is selected from thegroup consisting of hydrogen and methyl, R is phenyl or substitutedphenyl wherein the substitution is one or more of halogen, nitro, loweralkyl, cyclohexyl, alkoxy, naphthoxy or phenoxy and R and R are the sameor different and are lower alkyl of up to eight carbon atoms.

2. A compound according to claim 1 comprising 2-oxo-2-phenoxy-5-oxo-8,8-dimethy1-( 1,6-dioxa-2- phosphacyclononane).

3. A compound according to claim 11 comprising 2oxo-2-phenoxy-4-methyl-5-oxo-8,8-dimethyl-( 1,6-dioxa-Z-phosphacyclononane).

2. A compound according to claim 1 comprising2-oxo-2-phenoxy-5-oxo-8,8-dimethyl-(1,6-dioxa-2-phosphacyclononane). 3.A compound according to claim 1 comprising2-oxo-2-phenoxy-4-methyl-5-oxo-8,8-dimethyl-(1,6-dioxa-2-phosphacyclononane).